ASTM A387 Gr.5 Gr.11 Hydrogen-Resistant Steel Plate

ASTM A387 Grade 5 and Grade 11 hydrogen-resistant steel plates are chromium-molybdenum alloy pressure vessel steels manufactured in accordance with ASTM A387/A387M and the corresponding ASME SA-387 specifications. These grades are widely utilized in high-temperature, high-pressure equipment requiring stable mechanical properties and reliable performance in hydrogen service.

Unlike conventional carbon steel pressure vessel plates, Cr-Mo alloy steels leverage chromium (Cr) and molybdenum (Mo) alloying elements to enhance elevated-temperature strength, oxidation resistance, and microstructural stability during long-term service. This makes ASTM A387 Grade 5 and Grade 11 ideal materials for applications such as hydroprocessing reactors, hydrogenation reactors, heat exchangers, and refinery pressure vessels.

ASTM A387 grades are categorized into two classes-Class 1 and Class 2:

• Class 1: Has lower tensile strength requirements compared to Class 2.
• Class 2: Has higher mechanical property requirements and is typically used for more demanding pressure vessel applications.

What is ASTM A387 Gr.5?

ASTM A387 Grade 5 is a 5Cr-1/2Mo alloy steel plate. Its higher chromium content provides superior high-temperature oxidation resistance compared to lower-alloy pressure vessel steels, contributing to enhanced stability under elevated-temperature operating conditions.

What is ASTM S387 Gr.11?

ASTM A387 Grade 11 is a 1-1/4Cr-1/2Mo alloy steel plate and stands as one of the most widely specified Cr-Mo pressure vessel materials in petrochemical applications. It delivers an optimum balance of mechanical strength, weldability, fabricability, and cost-effectiveness.

GNEE Steel supplies steel plates compliant with ASTM A387 Gr.5 and Gr.11 standards, offering comprehensive quality documentation, custom cutting services, and inspection support to meet global requirements for pressure vessel manufacturing.

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1. The Role of Chromium (Cr) in Hydrogen Service
Chromium is a vital alloying element in ASTM A387/A387M Grade 5 and Grade 11 plates. The addition of chromium primarily enhances the elevated-temperature performance of the steel.

• Enhanced Oxidation Resistance: Chromium promotes the formation of a highly stable oxide layer on the steel surface at elevated temperatures, thereby minimizing oxidation tendencies and reinforcing material stability under elevated-temperature conditions.
• Improved Elevated-Temperature Stability: Higher chromium content aids in sustaining microstructural stability during long-term service at elevated temperatures. This explains why ASTM A387 Grade 5, with a nominal chromium content of approximately 5%, is preferentially specified over lower-chromium Cr-Mo steels for applications demanding superior oxidation resistance.
• Superior Surface Protection: The chromium-bearing oxide scale improves both the adhesion and the protective capability of surface oxidation products, effectively mitigating excessive scaling or oxidation during extended operational cycles.

2. The Role of Molybdenum (Mo) in Hydrogen Service
Molybdenum is another critical alloying element in Cr-Mo pressure vessel steels. Both our ASTM A387 Grade 5 and Grade 11 contain approximately 1/2% Mo, which significantly bolsters high-temperature mechanical properties.

• Elevated-Temperature Strength: Molybdenum helps maintain yield strength and tensile strength at elevated temperatures, enabling pressure vessel components to withstand severe operating conditions.
• Increased Resistance to Softening: Prolonged exposure to high-temperature environments can induce microstructural alterations in steel, resulting in a loss of strength. Molybdenum assists in maintaining structural stability and repressing the tendency toward strength degradation during service.
• Enhanced Long-Term Reliability: The synergistic combination of chromium and molybdenum provides a robust and stable alloy matrix, making Cr-Mo steels the industry standard for reactors, heat exchangers, and other refinery equipment operating under elevated-temperature conditions.

3. Operational Considerations for Cr-Mo Steels in Hydrogen Service
Hydrogen environments, particularly under high-temperature and high-pressure conditions, can trigger material degradation mechanisms that must be rigorously addressed during equipment design.

• Prevalent Damage Mechanisms Include: High-Temperature Hydrogen Attack (HTHA), decarburization, and a loss of tensile properties.

Mill Test Certificate

GNEE Steel supplies hydrogen-resistant steel plates compliant with ASTM A387 Gr.5 and Gr.11 standards, offering comprehensive quality documentation-including Material Test Certificates (MTC) and inspection support-as well as customized processing services for refineries, petrochemical plants, and pressure vessel manufacturing projects.

Typical Applications of ASTM A387 Gr.5 Gr.11 Hydrogen-Resistant Steel Plate

1. Hydroprocessing Reactors
2. Hydrocrackers
3. Hydrogen Reformers
4. Heat Exchangers
5. Pressure Vessels
6. Boilers
7. Petrochemical Equipment

 

Heat Treatment of ASTM A387 Gr.5 Gr.11 Hydrogen-Resistant Steel Plate

 

Our ASTM A387/A387M Grade 5 and Grade 11 steel plates are typically supplied in the normalized and tempered (N&T) condition.

This heat treatment process serves to:

Achieve a homogeneous microstructure

Meet specified tensile and yield strength requirements

Enhance toughness and fabricability

Maintain microstructural stability during elevated-temperature operations

Custom Cutting and Processing Services
Different pressure vessel projects require specific steel plate dimensions and processing conditions. To enhance processing efficiency, GNEE Steel offers customized processing services.
Available services include:
 Flame cutting
 CNC cutting
 Edge preparation and beveling
 Surface treatment

Comprehensive Mill Test Certificates (MTC) and Material Traceability
GNEE Steel provides:
 Mill Test Certificates (EN 10204 3.1)
 Heat number traceability
 Chemical composition reports
 Mechanical test results
 Heat treatment records
The provided documentation enables customers to verify that the ASTM A387 Gr.5 and Gr.11 steel plates comply with specified material standards and project requirements.

Need ASTM A387 Gr.5 or Gr.11 plates cut to your required dimensions with complete EN 10204 3.1 certification? Send us your plate size and project requirements for a customized quotation.

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FAQ

Q: A387 Gr.5 vs Gr.11: Which has higher chromium content?
A: A387 Grade 5 has a significantly higher chromium content than Grade 11. Grade 5 contains 4.00% to 6.00% chromium, whereas Grade 11 typically contains only 0.94% to 1.56% chromium. This increased chromium significantly boosts Grade 5's high-temperature oxidation and corrosion resistance.

Q: Which grade offers better high-temperature oxidation resistance, A387 Gr.11 or Gr.22?
A: ASTM A387 Grade 22 offers superior high-temperature oxidation resistance compared to Grade 11. This is primarily because Grade 22 features a higher chromium and molybdenum content (2.25% Cr and 1.0% Mo) than Grade 11 (1.25% Cr and 0.5% Mo), which allows it to form a more robust protective oxide layer at elevated temperatures.

Q: Which grade is better for hydrogen service, A387 Gr.5 or Gr.91?
A: ASTM A387 Grade 91 is significantly better than Grade 5 for high-temperature, high-pressure hydrogen service. While both materials resist High-Temperature Hydrogen Attack (HTHA), ASTM A387 Grade 91 offers vastly superior strength and corrosion resistance. It handles extreme operational envelopes far more effectively.

Q: What is the difference between ASTM A387 Grade 5 and Grade 11?
A: The primary differences between ASTM A387 Grade 5 and Grade 11 lie in their chromium content, corrosion resistance, and operational temperature limits. Both are chromium-molybdenum (chrome-moly) alloy steels used in pressure vessels and boilers, but they serve distinct industrial environments.